Existing stereo coding methods include intensity stereo, BCC (Binaual Cure Coding), and a PS (Parametric-Stereo coding) coding method, and in a general case, when the intensity coding is used, it is needed to extract an ILD (InterChannel Level Difference) parameter, use the ILD parameter as side information to perform coding, and transmit it preferentially to a decoding end for helping to restore a stereo signal. An ILD is a ubiquitous signal characteristic parameter that reflects a sound field signal, and the ILD can well embody sound field energy; however, sound fields of background space and left and right directions often exist in stereo, and a manner of only transmitting the ILD to restore the stereo no longer meets the requirement of restoring an original stereo signal. Therefore, a solution of transmitting more parameters to better restore the stereo signal is proposed, in addition to extracting the most basic ILD parameter, transmitting an interchannel phase difference (IPD: InterChannel Phase Difference) of a left channel and a right channel, and an interchannel cross correlation (ICC) parameter of the left channel and the right channel are also proposed, sometimes an overall phase difference (OPD) parameter of the left channel and a down-mix signal may also be included, and these parameters which reflect sound field information of the background space and left and right directions in the stereo signal and the ILD parameter are together used as the side information for coding and sent to the decoding end to restore the stereo signal.
The coding bit rate is an important factor for evaluating multimedia signal coding performance, and an adoption of a low bit rate is a goal that is pursued in common in the industry. An existing stereo coding technology definitely needs to improve the coding bit rate when transmitting the ILD as well as transmitting the IPD, ICC and OPD parameters at the same time, because the IPD, ICC and OPD parameters are local characteristic parameters of a signal that are used to reflect sub-band information of the stereo signal. Coding of the IPD, ICC and OPD parameters of the stereo signal needs to code the IPD, ICC and OPD parameters for each sub-band of the stereo signal, and for each sub-band of the stereo signal, IPD coding for each sub-band needs multiple bits, ICC coding for each sub-band needs multiple bits, and the rest may be deduced by analogy. Therefore, the stereo coding parameters need a large number of bits to enhance sound field information, but only part of the sub-bands can be enhanced at a lower bit rate, which cannot achieve a living restore effect. As a result, stereo information restored at the low bit rate and an original input signal have a great difference, which may bring extremely uncomfortable listening experience to a listener in term of a sound effect.